Creamy Onion Tart with Olives

Makes one 12-inch tart

I KNOW A WOMAN who never cooks the same thing twice for guests. She keeps a journal noting when and to whom she served each particular dish, ensuring there are never any repeats. I’m sort of in awe of her record-keeping, especially since I can’t recall what I ate for breakfast by the time dinner rolls around, but her method is antithetical to my own; I believe in repeats, in making a dish so often and for so many people that it becomes inextricably linked to you, something friends request and look forward to eating or want the recipe for. Your culinary calling card, so to speak.

My friend Nan Duffly believes in repeats too, and every year around the holidays, she hosts an open house at which she serves the same dishes, including a spiced, cured beef tenderloin, cooked rare and sliced thin, and a version of this exceptional onion tart.

The recipe was originally published in the Boston Globe; Nan adapted it slightly and I have adapted it a bit more, adding a briny olive topping that complements the sweet onions and flaky pastry, but it’s awesome even without that flourish. It has enough custard to bind it but not so much that it detracts from the onions. I like the mellow sweetness of white onions in this recipe, but you can substitute yellow instead.

Adding a bit of shortening to the pastry makes it especially flaky (come at me, haters), but you could use all butter or substitute lard or bacon fat for the shortening.

FOR THE CRUST:

5 tablespoons cold unsalted butter, cut into small cubes

1½ cups all-purpose flour

¼ teaspoon kosher salt

3 tablespoons vegetable shortening, lard, or cold bacon fat

1 large egg

2 to 3 tablespoons ice water

FOR THE TART:

4 tablespoons unsalted butter

3 large white onions, peeled and thinly sliced

¼ teaspoon sugar

Kosher salt and freshly ground black pepper

½ cup heavy cream

1 egg

2 anchovy fillets

1 clove garlic, peeled

½ cup olives, black or green, pitted and chopped

1 teaspoon thyme leaves, chopped

3 tablespoons extra-virgin olive oil

FOR THE CRUST: Spread the cubed butter in a small dish in a single layer and freeze until very cold, 15 minutes. In a food processor, pulse the flour and salt until blended. Add butter and shortening and pulse until the butter chunks are about the size of peas. In a small bowl, lightly beat the egg and 2 tablespoons of the ice water. Add the egg mixture to the food processor and pulse just until the mixture holds together in a shaggy ball (you may need to add the additional tablespoon water).

Turn the dough out onto a sheet of plastic wrap, use the plastic wrap to gather the dough into a ball, then flatten it into a disk with the heel of your hand. Tightly wrap and chill at least 1 hour and up to 3 days. (The dough can be frozen for up to a month. Let thaw overnight in the refrigerator before using.)

FOR THE FILLING: In a large frying pan, heat the butter over medium heat until it melts. Add the sliced onions and sugar and cook, stirring occasionally, until all the liquid has evaporated, about 15 to 20 minutes. The onions should be soft and light golden brown. Season to taste with salt and pepper. Remove from the heat, transfer to a bowl, and let cool. In a small bowl, whisk together the cream and egg. When the onions are cool, add the cream mixture and stir to combine.

Preheat the oven to 400°F. Remove the dough from the refrigerator and let stand 5 minutes. Unwrap and, on a lightly floured surface with a lightly floured rolling pin, roll dough into a 14-inch circle. Use a paring knife to trim the shaggy edges. Transfer to a parchment-lined baking sheet. Top with the onion mixture, spreading in an even layer and leaving a 1½-inch border. Fold the border over and pleat and crimp to create a crust. (If you’re making this tart for stand-up eating, roll the dough into a large rectangle instead of a circle, and cut it into squares after it’s baked.) Transfer to the oven and bake until the crust is a deep golden brown, about 45 minutes. Remove from the oven and let cool.

In a mortar and pestle, pound the anchovy fillets and garlic to a paste (if you don’t have a mortar and pestle, you can finely mince the anchovies and garlic and then use the side of your knife to grind into a paste). Transfer to a bowl and stir in the olives, thyme leaves, and olive oil. Dot the olive mixture evenly over the surface of the tart, then cut it into wedges and serve.